Xshell - a general purpose expert system shell

Abstract

Abstract : An expert system shell is a computer program which is ideally independent of the domain (subject) of application. A problem is represented by facts and rules which the shell processes as data. Although it may be large, the shell is a conventional procedural program. The shell described in this paper is the result of a study of existing shells and of the needs of the Intelligent Frequency Management System. The outcome is a comprehensive tool for the development, execution and maintenance of rule-based expert systems. Several unique features can ensure a high level of completeness, reliability and maintainability in the application. The degree of detail which follows is provided not only as a guide to users but also as a reference for the assessment of specification of other shells. This issue refers to XSHELL version 2.11. Expert systems usually divide the rules and facts into the domain, which describes the general case, and the context, which is the part that can vary from one problem to another. In XSHELL, facts and rules describe the problem domain. The assignment of certainties and values to the facts describes the context. The solution of problems is goal driven using a combination of backward and forward chaining. Each fact is described by a text. Associated with each fact is either a set of descriptive states each having a probability (certainty) , or a numeric value (or array of values). I refer to the descriptive facts as being qualified and the numeric facts as quantified. Rules consist of fact tests (the IF or condition part) and fact assignments (the THEN or consequence part). (kr)